Gas dispersion type anode structure for molten salt electrolysis

Abstract

The invention belongs to the technical field of electrolysis, and relates to a gas dispersion type anode structure for molten salt electrolysis. The anode structure comprises a graphite anode body, and a pile head area is arranged on the upper portion of the graphite anode body and used for bearing installation loads. The middle part of the graphite anode body is an exposed area which is connected with the pile head area and the dipping area, and the exposed area is provided with at least one air outlet; the lower part of the graphite anode body is a dipping area, and a gas inlet and a guide structure are arranged in the dipping area and are used for controlling gas to be smoothly guided into the anode and promoting the gas to be effectively discharged from the gas discharge port. The thickness of an electrolytic reaction anode inflation layer can be effectively reduced; according to the graphite anode with the gas inlets, the plurality of gas inlets are utilized, so that the loss caused by secondary reaction of chlorine and liquid metal is remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolysis and relates to a gas-dispersed anode structure for molten salt electrolysis. Background Art

[0002] Light metals, with their advantages of light weight, high strength, excellent thermal conductivity, and corrosion resistance, are widely used in modern industrial production. With the continuous advancement of science and technology, the preparation and performance of light metal materials are also constantly improving, making them play an increasingly important role in aerospace, automotive manufacturing and other fields. These light metals mainly include active metals such as magnesium, sodium, and lithium. They are typically obtained by electrolyzing molten chloride using graphite as the anode electrode.

[0003] A chloride electrolyzer is where the electrolysis reaction occurs. Traditional chloride electrolyzers consist of an electrolysis zone and a product collection zone. The electrolysis zone is composed of multiple sets of sequentially arranged anodes and cathodes. A chloride melt is fed into the electrolyzer. Liquid metal is deposited at the cathode, while chlorine gas is deposited at the anode.

[0004] During the electrolysis reaction, chlorine gas will produce an aerated layer on the surface of the graphite anode. The thickness of the aerated layer seriously affects the efficiency of the electrolysis reaction. When the aerated layer is too thick, it will greatly increase the reaction overpotential, increase the reaction energy consumption, affect ion conduction, and reduce the reaction current efficiency. The main methods currently on the market or reported in the literature to improve the anode gas problem are: slotted anodes with shallow grooves on the anode surface. This type of design can guide bubbles to a certain extent, but it mainly acts on the surface and lacks internal guide structures and active introduction mechanisms for air inlets. The bubbles are still mainly near the anode-electrolyte interface, and have limited effect on significantly reducing the thickness of the aerated layer. Porous anodes that use porous graphite to allow gas to escape through micropores. However, the porous structure has low strength, the pores are easily blocked by the electrolyte, leading to failure, and the conductivity is generally lower than that of dense graphite. Summary of the Invention

[0005] In order to solve the above problems, the present invention aims to provide a gas-dispersed anode structure for molten salt electrolysis, namely, a technical solution of a hollow graphite anode with an air inlet, which adopts a partitioned guidance method and utilizes multiple air inlets to significantly reduce the thickness of the aerated layer; at the same time, the partitioned guidance method minimizes the restricted electrolyte circulation caused by changing the chlorine flow channel; in addition, the present invention is designed based on the flow field simulation results of the inter-electrode channel between the anode and the cathode, which reduces the design cost and makes the distribution of the air inlets more reasonable.

[0006] Technical solution of the present invention:

[0007] A gas-dispersed anode structure for molten salt electrolysis, the anode structure comprising a graphite anode body, the upper portion of the graphite anode body being a pile head area for bearing the installation load; the middle portion of the graphite anode body being an exposed area connecting the pile head area with an impregnation area, the exposed area being equipped with at least one gas outlet; the lower portion of the graphite anode body being an impregnation area, the impregnation area being provided with an air inlet and a guide structure for controlling the gas to be smoothly guided into the interior of the anode and promoting the effective discharge of the gas from the gas discharge port.

[0008] Furthermore, the impregnation zone regulates the flow path of the gas inside the anode through the guide structure to maintain high efficiency and stability of the electrolysis process.

[0009] Furthermore, the density of the gas inlets between the upper and lower parts of the impregnation zone is varied in a uniform gradient, nonlinearly or segmented manner to achieve better gas distribution uniformity.

[0010] Furthermore, the shapes of the air inlet and the air outlet can be rectangular, circular, elliptical or other polygonal shapes to adapt to different gas flow requirements and installation conditions, thereby optimizing gas flow.

[0011] Furthermore, the guide groove of the guide structure has a width of 2mm to 8mm and a depth of 2mm to 8mm to ensure the smoothness of bubble segmentation and rising.

[0012] Furthermore, the guide grooves are symmetrically distributed on two inner surfaces of the hollow anode.

[0013] Furthermore, the shape of the guide groove is designed to be selected from a straight line, a broken line, an S-shaped bend or a spiral to adapt to different electrolyte flow characteristics and gas discharge requirements.

[0014] Furthermore, the material of the pile head area is selected from high-density, high-strength graphite material, or a composite structure of a graphite matrix inlaid with metal reinforcements to ensure structural stability and mechanical strength.

[0015] Furthermore, the high density is a density of 1.80-1.85 g / cm3, the high strength is a flexural strength of 22.5-23.5 MPa, and the compressive strength is 29.3-31.1 MPa.

[0016] Furthermore, the pile head area is provided with wiring holes and installation holes.

[0017] The sizes of the gas outlet and the gas inlet are determined by CFD numerical simulation to ensure smoothness and effectiveness of gas discharge. Detailed description of the invention:

[0019] The present invention provides a hollow graphite anode with an air inlet, which is provided with a pile head area and an impregnation area in sequence from top to bottom, with an exposed area provided therebetween, which is used to connect the pile head area and the impregnation area, while ensuring that the gas can be discharged smoothly. The pile head area needs to bear the installation load, so a high-density, high-strength graphite material is selected, or a composite structure of a graphite matrix inlaid with metal reinforcements is adopted to ensure its excellent mechanical strength. The impregnation area is in direct contact with the corrosive molten salt electrolyte and participates in the electrochemical reaction, so it is subjected to a special impregnation treatment (see the patent CN 118479471 A disclosed by the inventor) to ensure its electrical conductivity, corrosion resistance and necessary mechanical strength.

[0020] The hollow graphite anode with an air inlet is provided with one or more arranged hollowed-out air inlets in the impregnation area. This air inlet structure not only effectively guides chlorine bubbles out of the anode interior, thereby reducing the thickness of the aerated layer and improving gas distribution, but also significantly reduces the contact area and contact time between chlorine and liquid metal, lowering the probability of secondary reactions of chlorine in the liquid metal, and improving the electrochemical performance and operational stability of the anode.

[0021] The hollow graphite anode with an air inlet has one or more arranged air outlets in the exposed area. The air outlets ensure that gas can be discharged smoothly from the interior of the anode, effectively avoiding blockage caused by gas accumulation.

[0022] The hollow graphite anode with an air inlet, whether it is the air inlet or the air outlet, can be designed into various forms according to specific process requirements, including but not limited to circular, elliptical, square, long strip or other polygonal shapes, to adapt to different gas flow requirements and installation conditions, thereby optimizing gas flow.

[0023] Preferably, in the impregnation area of ​​the hollow graphite anode, the gas content gradually increases as the interelectrode channel goes from bottom to top. For this reason, the gas inlets in the upper area can be appropriately densely arranged (preferably the previous row of gas inlets and the next row of gas inlets are densely arranged in proportion, such as 1:1.1, 1:1.15, 1:1.2) to improve the uniformity of gas distribution, enhance gas discharge efficiency, reduce the adverse effects of local gas accumulation on anode performance, and thus improve the stability and efficiency of the overall electrochemical reaction.

[0024] It is further preferred that the air inlet introduces bubbles into the internal rising channel of the anode, and the bubbles flow from bottom to top along the channel. The internal structure of the anode is reasonably designed (i.e., there are guide grooves), and guide grooves are provided to enable the gas to rise smoothly, avoid gas retention and aggregation, and promote the rapid discharge of bubbles. During the electrolysis process, the bubbles generated on the anode surface move upward under the action of buoyancy. The air inlet set in the anode impregnation area forms a local low-pressure area. Bubbles are actively "captured" and introduced into the interior of the anode under the drive of pressure difference, avoiding random attachment, merging and growing of bubbles on the electrode surface. Bubbles on the surface of traditional solid anodes need to overcome the higher solid-liquid-gas three-phase line energy barrier before they can detach. The geometric configuration of the air inlet weakens the bubble adhesion (contact angle effect), making it easier for bubbles to detach from the electrode surface and enter the internal channel, reducing the residence time.

[0025] It is further preferred that the width of the guide groove is 2-8 mm and the depth is 2-8 mm, and the two inner surfaces of the hollow anode have a plurality of parallel concave straight lines, bends or S-shaped bends and other guide grooves that are symmetrically distributed. The shape and size of the grooves can be designed in various forms according to the specific anode structure and process requirements to meet different requirements. After the bubbles enter the guide grooves, they are subjected to the strong shearing action of the narrow groove walls and rupture. Large bubbles are divided into small bubble groups, which significantly increases the gas-liquid interface area. Small bubbles have higher internal pressure, are easier to move with the flow field and are not easy to merge. The physical constraints of the grooves force the bubbles to rise along a preset path. The damping effect of the groove wall suppresses vortex shedding and improves flow stability.

[0026] In the present invention, the short electrode width is selected from Example 1 (small groove), and the long electrode width is selected from Example 2 (large groove). If the electrode width is too long and the rectangular shape is still used, it may cause uneven current density distribution on the electrode surface, affecting electrolysis efficiency and thus affecting the generation of gas on the electrode surface.

[0027] Compared with the prior art, the present invention has the following positive effects:

[0028] (1) The present invention can effectively reduce the thickness of the anode gas filling layer of the electrolysis reaction; (See Figure 5 , describing the thickness of the aerated layer in the inter-electrode channel of the cathode and anode in the top area of ​​the electrode. The former is before optimization, and the latter is after optimization with the air inlet opened.

[0029] (2) The graphite anode with air inlets of the present invention utilizes multiple air inlets to significantly reduce the loss caused by the secondary reaction between chlorine and liquid metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the three-dimensional structure of a (rectangular air inlet) graphite anode of the present invention.

[0031] Figure 2This is a schematic diagram of the three-dimensional structure of a (circular air inlet) graphite anode of the present invention.

[0032] Figure 3 This is a schematic diagram of the three-dimensional structure of a graphite anode (with internal guide grooves) according to the present invention.

[0033] Figure 4 This is a partial schematic diagram of the diversion groove.

[0034] Figure 5 A cloud diagram describing the thickness of the gas-filled layer in the inter-electrode channel of the cathode and anode in the top area of ​​the electrode.

[0035] In the figure, 1-pile head area; 2-exposed area; 3-immersion area; 4-wiring hole; 5-mounting hole; 6-rectangular air inlet; 7-circular air inlet; 8-rectangular air outlet; 9-diversion groove. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the features and advantages of the present invention can be more clearly understood.

[0037] A gas-dispersed anode structure for molten salt electrolysis, the anode structure comprising a graphite anode body, the upper portion of the graphite anode body being a pile head area for bearing the installation load; the middle portion of the graphite anode body being an exposed area connecting the pile head area with an impregnation area, the exposed area being equipped with at least one gas outlet; the lower portion of the graphite anode body being an impregnation area, the impregnation area being provided with an air inlet and a guide structure for controlling the gas to be smoothly guided into the interior of the anode and promoting the effective discharge of the gas from the gas discharge port.

[0038] Furthermore, the impregnation zone regulates the flow path of the gas inside the anode through the guide structure to maintain high efficiency and stability of the electrolysis process.

[0039] Furthermore, the density of the gas inlets between the upper and lower parts of the impregnation zone is varied in a uniform gradient, nonlinearly or segmented manner to achieve better gas distribution uniformity.

[0040] Furthermore, the shapes of the air inlet and the air outlet can be rectangular, circular, elliptical or other polygonal shapes to adapt to different gas flow requirements and installation conditions, thereby optimizing gas flow.

[0041] Furthermore, the guide grooves of the guide structure have a width of 2mm to 8mm and a depth of 2mm to 8mm to ensure smooth bubble segmentation and rise. The guide grooves are symmetrically distributed on both surfaces of the hollow anode. The shape of the guide grooves can be selected from straight lines, broken lines, S-shaped bends, or spirals to accommodate different electrolyte flow characteristics and gas emission requirements.

[0042] Furthermore, the pile head area is constructed from high-density, high-strength graphite, or a composite structure featuring a graphite matrix embedded with metal reinforcements, to ensure structural stability and mechanical strength. High density refers to a density of 1.80-1.85 g / cm³, while high strength refers to a flexural strength of 22.5-23.5 MPa and a compressive strength of 29.3-31.1 MPa. Wiring and mounting holes are provided in the pile head area.

[0043] Example 1:

[0044] In this embodiment, Figure 1 The impregnation area of ​​the hollow graphite anode adopts uniformly arranged rectangular air inlets, the long side of which is consistent with the flow direction of the interelectrode channel. In the upper area of ​​the impregnation area, the air inlets are locally encrypted according to the gas content distribution characteristics, and the distance between adjacent air inlets gradually increases from top to bottom to form a gradient layout. In the impregnation area, there are a total of 6 rectangular air inlets, the width of the rectangular air inlet is 40mm, and the length of the air inlet is 800mm. There is a rectangular air outlet in the exposed area. The long side design of the rectangular air inlet is conducive to guiding the chlorine to form a flat bubble flow with directional flow, reducing bubble merging. The encrypted area significantly improves the gas discharge efficiency by increasing the density of the air inlet, which greatly reduces the thickness of the aerated layer. At the same time, the uniformity of the upper gas distribution is significantly improved, which effectively alleviates the decrease in current efficiency caused by overvoltage. (See Figure 5 Cloud diagram describing the thickness of the gas-filled layer in the inter-electrode channel between the cathode and anode in the top area of ​​the electrode)

[0045] Example 2:

[0046] In this embodiment, Figure 2 The impregnation area of ​​the hollow graphite anode adopts circular air inlets, which are arranged to form a honeycomb air-conducting network. The radius of the circular air inlets in the impregnation area is 20 mm, and there are 83 circular air inlets in total. There is a rectangular air outlet in the exposed area. The circular air inlets in the entire electrode are arranged in a staggered manner according to density to minimize the deviation of the anode current. The staggered layout promotes the formation of natural vortex convection of bubbles during the rising process, significantly shortening the residence time of chlorine between the electrodes and reducing the probability of contact with liquid metal, thereby greatly reducing secondary reaction losses. The axial symmetry of the circular air inlet enhances the adaptability of the anode to asymmetric flow fields, making it suitable for electrolysis environments under complex working conditions.

[0047] Example 3:

[0048] In this embodiment, Figure 3While rectangular air inlets are provided in the impregnation zone of the hollow graphite anode, guide grooves are also designed inside the anode. In the impregnation zone, there are a total of six rectangular air inlets, each 40mm wide and 800mm long. The exposed zone has a single rectangular air outlet. The guide grooves are distributed around the central axis of the anode with a specific width, precisely matching the position of the air inlet. After bubbles enter the guide grooves, they are sheared by the groove wall and divided into tiny bubble groups, rising steadily along the groove path. This structure significantly improves the separation efficiency of the gas-liquid two-phase flow and effectively controls the thickness of the aeration layer.

[0049] In this embodiment, Figure 4 The width of the gas guide groove is 4 mm and the depth is 4 mm. There are a plurality of parallel and concave straight guide channels symmetrically distributed on the two inner surfaces of the hollow anode.

[0050] The working process of the present invention is as follows:

[0051] During the electrolysis process, the graphite block portion 3 with the flow groove immersed in the electrolyte generates bubbles. The design of the gas flow groove allows the bubbles to rise stably in the graphite block. The rational design of the width and angle of the bubbles in the flow groove helps to reduce the oscillation and instability of the bubbles, while extending the residence time of the bubbles in the flow groove, effectively reducing the generation of large bubbles. This design can also improve the stability and uniformity of the bubbles, allowing the bubbles to move more smoothly and reducing the resistance of the bubbles. Ultimately, this design helps to improve the current efficiency and the yield of chlorine.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and modifications without departing from the concept of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A gas-dispersed anode structure for molten salt electrolysis, characterized in that: The anode structure includes a graphite anode body, the upper part of the graphite anode body is a pile head area, which is used to bear the installation load; the middle part of the graphite anode body is an exposed area, which connects the pile head area and the impregnation area, and the exposed area is equipped with at least one gas outlet; the lower part of the graphite anode body is an impregnation area, and the impregnation area is provided with an air inlet and a guide structure, which are used to control the gas to be smoothly guided into the interior of the anode and promote the effective discharge of the gas from the gas exhaust port.

2. The gas dispersion anode structure according to claim 1, wherein: The impregnation zone regulates the flow path of the gas inside the anode through the guide structure to maintain high efficiency and stability of the electrolysis process.

3. The gas dispersion anode structure according to claim 1 or 2, characterized in that: The density of the gas inlets between the upper and lower parts of the impregnation zone is varied in a manner selected from uniform gradient variation, nonlinear variation or segmented variation to achieve better gas distribution uniformity.

4. The gas dispersion anode structure according to any one of claims 1 to 3, wherein: The shapes of the air inlet and the air outlet can be rectangular, circular, elliptical or other polygonal shapes to adapt to different gas flow requirements and installation conditions, thereby optimizing gas flow.

5. The gas dispersion anode structure according to any one of claims 1 to 4, characterized in that: The guide groove of the guide structure has a width of 2mm to 8mm and a depth of 2mm to 8mm to ensure the smoothness of bubble segmentation and rising.

6. The gas dispersion anode structure according to claim 5, characterized in that: The guide grooves are symmetrically distributed on two inner surfaces of the hollow anode.

7. The gas dispersion anode structure according to claim 6, characterized in that: The shape of the guide groove is designed to be selected from a straight line, a broken line, an S-shaped bend or a spiral to adapt to different electrolyte flow characteristics and gas discharge requirements.

8. The gas dispersion anode structure according to any one of claims 1 to 7, wherein: The material of the pile head area is selected from high-density, high-strength graphite material, or a composite structure of a graphite matrix inlaid with metal reinforcements to ensure structural stability and mechanical strength.

9. The gas dispersion anode structure according to claim 8, characterized in that: The high density is 1.80-1.85 g / cm3, the high strength is 22.5-23.5 MPa in flexural strength and 29.3-31.1 MPa in compressive strength.

10. The gas dispersion anode structure according to claim 1, wherein: The pile head area is provided with wiring holes and installation holes.

Images